The popularity of small portable audio appliances and the ability to exchange audio information across the Internet have driven recent efforts to develop compression standards for storing, transferring, and playing back high fidelity audio information. Two of the more advanced of these audio compression standards are the Moving Pictures Expert Group Layer 3 (MP3) and the Advanced Audio Coding (AAC) standards.
Generally, the MP3 and AAC standards define audio decoding techniques that reduce the sampling rate and sample resolution of a stream of digitized audio data for storage and transmission. While these standards define a number of stream parameters, such as the input sampling rates and stream format, they otherwise allow significant flexibility in the implementation of the actual encoders and decoders.
In designing MP3 and AAC audio encoders and decoders, efficient encoding and decoding techniques are required for compressing high-fidelity audio into the smallest possible compressed digital files and subsequently reconstructing that high-fidelity audio from the compressed digital files without significant noise and distortion. Further, these audio techniques should minimize the overall complexity of the hardware and software designs, while at the same time being sufficiently flexible for utilization in a range of possible applications.